CDF plots with priors show the PDF

The 1D CDF plots, if generated with priors=True will overplot the pdf, e.g.

added Bug label

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assigned to @gregory.ashton

created merge request !538 (merged) to address this issue

mentioned in merge request !538 (merged)

closed via merge request !538 (merged)

mentioned in commit 0998b75b

unassigned @gregory.ashton